1. Field of the Invention
The field of the invention is those devices which stabilize a hollow workpiece as the workpiece is rotated in a chuck and machined. More particularly the field of the invention is such devices which stabilize a workpiece having a tubular portion, as it is being sawed or cut into a plurality of annular rings.
2. Description of the Prior Art
Numerous devices have been employed in the prior art to stabilize a rotating, hollow workpiece during a machining operation. U.S. Pat. No. 3,289,505 to Pyke and U.S. Pat. No. 3,422,709 to Rees illustrate two such devices which accomplish centering of the tubular workpiece with three radial projections that engage with the interior surface of the workpiece.
There are also various devices which incorporate means to expand the stabilizing device after they have been inserted within the workpiece. In U.S. Pat. No. 2,453,717 to Long is disclosed one such device in which a plurality of wedges are moved to expand the effective diameter of the stabilizing device and to engage the interior suface of the workpiece. In U.S. Pat. No. 2,659,260 to Layne et al. is disclosed another such work holding device which engages the interior surface of the workpiece by moving wedges which increase the effective diameter of the device.
In U.S. Pat. No. 2,686,681 is disclosed a device for holding a workpiece which incorporates a flexible metal diaphragm having a frustoconical shape. Axial pressure is applied to the diaphragm, causing it to flex and thus expand its effective diameter.
In U.S. Pat. No. 2,851,916 to Grandy is disclosed an example of a device which stabilizes a tubular workpiece during machining by means of hydrolics. These devices are typically elaborate and cumbersome in operation.
Arbors have generally not been used to stabilize tubular workpieces during a cutting procedure wherein the tubular workpiece is being cut into a plurality of annular rings. A common technique, currently used, is to employ a multiple cut saw having a plurality of circular saws which successively have slightly smaller diameters. By using such a multiple cut saw, a plurality of rings can be cut off of a tubular workpiece in one operation, without the use of a stabilizing device. Because the saw blades are staggered, each ring is cut off successively as each saw cuts through the workpiece. This type of multiple cut saw allows a substantial increase in efficiency. However, there is a tendency for burrs to develop when the last portion of each ring is being cut, and there is also occasional damage to the saw blades.
A mechanism for cutting tubular lengths which does not utilize a stabilizing arbor is disclosed in U.S. Pat. No. 3,797,338 to Molnar. In the Molnar devices, lengths of tubing are revolved around a drum and are separated into selected lengths by a saw. This type of mechanism is not suited for use where various machining operations are performed prior to the sawing operation.
In U.S. Pat. No. 4,126,064 to Tarrant is disclosed a machine which cuts an annular piece from tubular stock. The Tarrant device is useful in preventing the development of burrs and does not incorporate a stabilizing arbor. However, the Tarrant device involves a somewhat complicated procedure and only cuts off one annular piece at a time.
Arbors have not been generally adaptable for use in stabilizing a tubular workpiece during an operation which cuts a plurality of rings in a single procedure. Arbors of the prior art are generally not easy to repeatedly insert and remove in a simple motion; they do not have properties that would prevent the development of burrs when a saw cuts through the workpiece; and they would not be able to withstand damage caused by the saw blades cutting too deeply.
It is also preferable for the stabilizing device to provide support along the entire length of the tubular workpiece upon which the cutting operation is being performed. This is so that the stabilization of the workpiece is not dependent upon the precise location of the arbor or upon the order in which the annular rings are cut off and so that the individual rings are supported as the saws cut through the workpiece.
In U.S. Pat. No. 3,118,683 to Hoshizaki is disclosed an arbor which is more particularly adaptable to a multiple cutting operation than most arbors because it can be repeatedly inserted and removed in a simple motion. In the Hoshizaki device, balls are retained in longitudinal grooves in a substantially cylindrical arbor. Upon insertion within a tubular workpiece, the balls deform to accommodate the inside diameter of the tube and roll along the grooves to aid in the insertion of the arbor. This arbor is insertable and removable in a simple operation. However, the Hoshizaki device is particularly susceptible to damage which may result if any of the cutting saws should penetrate too deeply. Also, the Hoshizaki device would not provide stabilizing support along the entire length of the workpiece during the cutting operation. This is undesirable because the stabilization of the workpiece should not be dependent upon the precise location of the arbor in relation the workpiece, and also because the separation between the workpiece and the arbor would have a tendency to cause burrs.